The accuser says he was sexually assaulted after Mass in 1997 by the Rev. Andrew McCormick.
McCormick was suspended from the Philadelphia archdiocese over a less serious allegation when he was arrested in 2012.
The 57-year-old priest's lawyer says the charges stem from one encounter with a lone accuser.
Philadelphia prosecutors have been investigating priest-abuse reports in Philadelphia for a decade, and have gained several sex-abuse convictions.
Authorities say McCormick regularly took boys on trips to Poland during his three decades as a Philadelphia-area priest.
The trial accuser says he was assaulted at St. John Cantius in northeast Philadelphia.